Belt conveyance apparatus including a belt and a driving roller in an image forming apparatus or system

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application 2013-152864, filed on Jul. 23, 2013, which claims priority to Japanese Patent Application 2012-170634, filed on Jul. 31, 2012, the entire contents of both are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a belt conveyance apparatus, an image forming apparatus, and an image forming system.

2. Description of the Related Art

In an apparatus which moves a belt by a driving roller, there is known a technology of controlling the belt surface speed based on detection of two sensors. One sensor of the two sensors detects the rotation speed of the driving roller, and another sensor detects the belt surface speed.

JP-A No. 2004-220006 discloses an image forming apparatus for controlling a belt speed by a secondary control loop which uses a second sensor to detect rotation speed of a driving roller, when a primary control loop which uses a first sensor to detect a belt surface speed is abnormal. When the primary control loop is abnormal because of dirt and there is expansion of the driving roller due to a rising temperature, the image forming apparatus is not controlled accurately. In this case the image forming apparatus needs to stop operation.

SUMMARY OF THE INVENTION

The embodiments of the present invention have been developed in view of the above-described problems of the conventional techniques.

An objective of the embodiments of the present invention is to provide a belt conveyance apparatus, an image forming apparatus and an image forming system that can prevent reduction of accuracy of controlling the belt surface speed when a sensor to detect the belt speed is abnormal.

In one aspect, a belt conveyance apparatus including a driving roller to rotate and drive a belt, a first detector to detect surface speed of the belt, and a second detector to detect rotation speed of the driving roller. There is a first calculator to calculate a first deviation from target speed based on the surface speed and the target speed, and a memory to store a correction value corresponding to the first deviation. There is a second calculator to calculate a second deviation from the target speed corrected by the first deviation based on the target speed, the first deviation and the rotation speed of the driving roller. A controller controls the rotation speed of the driving roller based on the second deviation. There is also a switch to switch the first deviation to the correction value stored in the memory when controller judges that the first detector is abnormal.

The invention can also be used in an image forming system which includes an image forming apparatus.

According to the embodiments of the present invention, the belt conveyance apparatus, the image forming apparatus and the image forming system are provided in order to prevent reducing accuracy of controlling the belt surface speed when a sensor to detect the belt speed is abnormal.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

<figref idref="DRAWINGS">FIG. 1</figref> is a schematic configuration view showing an example of the image forming system which includes an image forming apparatus;

<figref idref="DRAWINGS">FIG. 2</figref> is a schematic configuration view showing an example of an intermediate transfer unit together with various units of the image forming apparatus;

<figref idref="DRAWINGS">FIG. 3</figref> is a functional block diagram showing an example of a belt driving controlling unit which controls an intermediate transfer belt together with various units of the image forming apparatus according to an embodiment of the present invention;

<figref idref="DRAWINGS">FIGS. 4A-4C</figref> are illustrations showing influence in a case that the belt scale sensor does not detect the speed of the surface of the intermediate transfer belt;

<figref idref="DRAWINGS">FIG. 5</figref> is a functional block diagram showing an example of a controller together with various units of the image forming apparatus according to a first example of the present invention;

<figref idref="DRAWINGS">FIG. 6</figref> is a flowchart showing an exemplary operation by the controller according to the first example of the present invention.

<figref idref="DRAWINGS">FIG. 7</figref> is a flowchart showing an exemplary operation by the controller of the image forming apparatus according to the first example of the present invention when the belt scale sensor is abnormal.

<figref idref="DRAWINGS">FIG. 8</figref> is a functional block diagram showing an example of a controller together with various units of the image forming apparatus according to a second example of the present invention;

<figref idref="DRAWINGS">FIG. 9</figref> is a flowchart showing an exemplary operation by the controller according to the second example of the present invention.

<figref idref="DRAWINGS">FIG. 10</figref> is a flowchart showing an exemplary operation by the controller of the image forming apparatus according to the second example of the present invention when the belt scale sensor is abnormal.

<figref idref="DRAWINGS">FIG. 11</figref> is a functional block diagram showing an example of the belt driving controlling unit which controls the intermediate transfer belt together with various units of the image forming apparatus according to a modification example of the present invention;

<figref idref="DRAWINGS">FIGS. 12A and 12B</figref> are data tables stored in a memory according to a modification example of the present invention.

<figref idref="DRAWINGS">FIG. 13</figref> is a flowchart showing an exemplary operation by the controller based on average value of data A corresponding to each temperature range according to a modified example of the first example of the present invention.

<figref idref="DRAWINGS">FIG. 14</figref> is a flowchart showing an exemplary operation by the controller of the image forming apparatus according to the modified example of the first example of the present invention when the belt scale sensor is abnormal.

<figref idref="DRAWINGS">FIG. 15</figref> is a flowchart showing an exemplary operation by the controller based on average value of data B corresponding to each temperature range according to a modification example of the second example of the present invention.

<figref idref="DRAWINGS">FIG. 16</figref> is a flowchart showing an exemplary operation by the controller of the image forming apparatus according to the modified example of the second example of the present invention when the belt scale sensor is abnormal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be explained by describing the image forming system. This invention can be also applied to any image forming apparatus having a belt unit such as a facsimile device, a copier device, a multi-function peripheral, or the like, otherwise than as specifically described herein.

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, an image forming system <b>1000</b> including an image forming apparatus <b>100</b>. As shown in <figref idref="DRAWINGS">FIG. 1</figref>, an image forming apparatus <b>100</b> according to an embodiment includes a scanner unit <b>5</b>, an image forming unit <b>6</b>, a photoconductive unit <b>3</b>, a developing unit <b>4</b>, an intermediate transfer unit <b>2</b>, a feeding unit <b>1</b>, a conveyance unit <b>11</b>, and a fixing unit <b>7</b>. The scanner unit <b>5</b> emits light to a document, and reads image data by receiving reflecting light from the document. An image processing unit of the image forming apparatus is implemented as a processor, application specific integrated circuitry and/or other circuitry, and processes the image data using processes such as shading correction, gamma correction, or MTF correction, and sends the image data to the image forming unit <b>6</b>. The photoconductive drum of the photoconductive unit <b>3</b> rotates at constant speed. The image forming unit <b>6</b> drives a LD (Laser Diode) corresponding to the image data. The LD emits laser beam to the photoconductive drum, and writes an electrostatic latent image on the photoconductive drum.

The developing unit <b>4</b> develops the electrostatic latent image with toner into a toner image. The toner image on the photoconductive drum is transferred to an intermediate transfer belt of the intermediate transfer unit <b>2</b>. In the case of a full-color copy, four toner images (black, cyan, magenta, and yellow) are transferred to an intermediate transfer belt in succession. The feeding unit <b>2</b> feeds a sheet such as paper into the image forming apparatus. The sheet is conveyed to secondary transfer point. There are a secondary transfer roller and a transfer facing roller at on the secondary transfer point. These four toner images are transferred to the sheet between the secondary transfer roller <b>9</b> and the transfer facing roller <b>10</b>. The conveyance unit <b>11</b> conveys the sheet on which is transferred toner image to the fixing unit <b>7</b>. The fixing unit <b>7</b> fixes the toner image to the sheet with heat and pressure by a fixing roller and a pressure roller. Then, image forming apparatus <b>100</b> discharges the sheet on which the toner image was formed.

The image forming apparatus <b>100</b>, according to this embodiment, can be connected to a DFE <b>12</b> (Digital Front End) via a dedicated communication line <b>13</b>. The DFE <b>12</b> can include a function of Raster image processor (RIP) and generate raster image data based on image data receiving from a PC (Personal Computer). Then, the DFE <b>12</b> can send the raster image data to the image forming apparatus <b>100</b>.

Additionally, the DFE <b>12</b> may connect to the image forming apparatus <b>100</b> via a network. Alternatively, the DFE <b>12</b> may be omitted as an exterior element, and the image forming apparatus <b>100</b> may include the function of the DFE inside and generate the raster image data based on the image data received from the PC.

<figref idref="DRAWINGS">FIG. 2</figref> is a schematic configuration view showing the intermediate transfer unit <b>2</b> together with various units of the image forming apparatus <b>100</b> shown in <figref idref="DRAWINGS">FIG. 1</figref>. The intermediate transfer unit <b>2</b> includes the intermediate transfer belt <b>19</b>, a driving roller <b>16</b>, a following roller <b>17</b>, the transfer facing roller <b>10</b>, and a tension roller <b>18</b>. The intermediate transfer belt <b>19</b> is wound around the driving roller <b>16</b>, the following roller <b>17</b>, and the transfer facing roller <b>10</b>. The tension roller <b>18</b> applies tension to the intermediate transfer belt <b>19</b>. The intermediate transfer belt <b>19</b> is moved by the driving roller <b>16</b> which is rotated by a motor <b>14</b>. There is a speed reduction mechanism <b>15</b> such as gears between the motor <b>14</b> and the driving roller <b>16</b>. The rotation speed of the motor <b>14</b> is reduced by the speed reduction mechanism <b>15</b>, and is transmitted to the driving roller <b>16</b>.

There is an encoder pattern (belt scale) on almost the entire back surface of the intermediate transfer belt <b>19</b>. A belt scale sensor <b>20</b> detects the belt scale, for example using light which is emitted, reflected off the transfer belt <b>19</b>, and received by a sensor. The belt scale sensor <b>20</b> is an example of the first detecting unit. There is an encoder <b>21</b> for detecting the rotation speed of the driving roller <b>16</b> on the shaft of the driving roller <b>16</b>. The encoder <b>21</b> may be rotary encoder, and may detect the rotation speed of the driving roller <b>16</b> by a disk on the shaft of the driving roller <b>16</b> and a sensor detecting the disk. This sensor may operate by detecting reflected light, for example. The encoder <b>21</b> is an example of the second detecting unit. The surface speed of the intermediate transfer belt <b>19</b> is controlled to be a target speed based on the detection of the belt scale sensor <b>20</b> and the detection of the encoder <b>21</b>.

<figref idref="DRAWINGS">FIG. 3</figref> is a functional block diagram showing a belt driving controlling unit <b>22</b> which controls the intermediate transfer belt <b>19</b> together with various units. The belt driving controlling unit <b>22</b> includes a driver <b>25</b> which drive the motor <b>14</b>, a memory <b>26</b>, and a CPU <b>27</b>. The CPU <b>27</b> includes a controller <b>28</b> and an average value calculator <b>29</b>, and controls each part of the belt driving controlling unit <b>22</b>. The memory <b>26</b> stores the average value calculated by the average value calculator <b>29</b> or the like.

When a main controller <b>23</b> sends a start signal and a rotation direction indication signal or the like to the CPU <b>27</b> of the belt driving controlling unit <b>22</b>, the belt driving controlling unit <b>22</b> starts rotation of the motor <b>14</b> by the driver <b>25</b>. The controller <b>28</b> calculates based on the detection of the belt scale sensor <b>20</b> and the encoder <b>21</b>. Then, the controller <b>28</b> controls the motor <b>14</b> so that speed of surface of the intermediate transfer belt <b>19</b> is the target speed based on result of calculation.

<figref idref="DRAWINGS">FIGS. 4A-4C</figref> are illustrations showing an influence when the belt scale sensor <b>20</b> does not detect the speed of surface of the intermediate transfer belt <b>19</b> in the prior art. <figref idref="DRAWINGS">FIG. 4A</figref> is an illustration showing the intermediate transfer unit in a normal condition. <figref idref="DRAWINGS">FIG. 4B</figref> is an illustration showing the intermediate transfer unit when the driving roller <b>16</b> expands because of rising temperature. <figref idref="DRAWINGS">FIG. 4C</figref> is an illustration showing the speed of the surface of the intermediate transfer belt <b>19</b>. As shown in <figref idref="DRAWINGS">FIG. 4C</figref>, when the belt scale sensor <b>20</b> does not detect the speed of the surface of the intermediate transfer belt <b>19</b> and the driving roller <b>16</b> expands, and the speed of the surface of the intermediate transfer belt is faster than a normal condition. When the driving roller <b>16</b> contracts because of decreasing of temperature, the speed of the surface of the intermediate transfer belt <b>19</b> may decrease.

Next, a description will be given of an image forming apparatus of a first example of the present invention. <figref idref="DRAWINGS">FIG. 5</figref> is a functional block diagram showing a controller <b>28</b><i>a </i>together with various units of the image forming apparatus according to a first example.

The controller <b>28</b><i>a </i>corresponds to the controller <b>28</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>. As shown in <figref idref="DRAWINGS">FIG. 5</figref>, the controller <b>28</b><i>a </i>includes a first comparator <b>30</b> (the first calculator), an integrator <b>31</b>, a position controller <b>32</b>, a switching unit <b>33</b>, a second comparator <b>34</b> (the second calculator), a velocity controller <b>35</b>, and a PWM converter <b>36</b>.

The first comparator <b>30</b> receives the target speed of the surface of the intermediate transfer belt <b>19</b> and the detection of the belt scale sensor <b>20</b> which indicates belt scale speed, and calculates a velocity deviation of the belt scale speed from a target speed, for example, using subtraction. Then the first comparator <b>30</b> outputs the velocity deviation to the integrator <b>31</b>. The integrator <b>31</b> calculates the position deviation by integrating the velocity deviation, and outputs the position deviation to the position controller <b>32</b>. The position controller <b>32</b> calculates the correction value of the target speed as the speed deviation from the target speed corresponding to the position deviation.

When the belt scale sensor <b>20</b> is abnormal, the switching unit <b>33</b> switches the input terminal to Y from X. The switching unit <b>33</b> may be implemented using any desired technology including a programmed processor, an integrated circuit, circuit components, and/or a combination of these elements. The second comparator <b>34</b> receives the target speed, the detection of the encoder <b>21</b> (encoder speed), and signal via the switching unit <b>33</b>, and calculates a velocity deviation. The second comparator <b>34</b> outputs the velocity deviation to the velocity controller <b>35</b>.

The velocity controller <b>35</b> controls the output voltage which is output to the motor <b>14</b> corresponding to the velocity deviation from the second comparator <b>34</b> so that the surface speed of the intermediate transfer belt <b>19</b> approaches the target speed. The PWM converter <b>36</b> outputs pulses to the driver <b>25</b> corresponding to the controlling output voltage.

Additionally, the position controller <b>32</b> and the velocity controller <b>35</b> may be implemented as one or more general controller which is designed by frequency response based on the motor input voltage, the signal from the encoder, and the signal from the belt scale sensor <b>20</b>.

Next, a description will be given of an operation of the controller <b>28</b><i>a</i>. The integrator <b>31</b> of the controller <b>28</b><i>a </i>converts the velocity deviation which was calculated from the belt scale speed and the target speed (first target speed) received from the main controller <b>23</b> or CPU <b>27</b>, to the position deviation. The position controller <b>32</b> outputs the correction value corresponding to the position deviation. The sum of the correction value and the target speed (first target speed) is a rotating shaft target speed (second target speed). The velocity deviation is calculated based on the second target speed and the encoder speed. The velocity controller receives the velocity deviation, and outputs the controlling output voltage (indicated value). The PWM converter <b>36</b> outputs the pulse corresponding to the controlling output voltage, and drives the driver <b>25</b>.

When the belt scale sensor <b>20</b> is abnormal, the controller <b>28</b><i>a </i>controls the motor <b>14</b> without using the outputs from the position controller <b>32</b> by switching the input terminal to the Y position by the switching unit <b>33</b>. This enables the controller <b>28</b><i>a </i>to feedback control. Additionally, the loop of using the detection of the belt scale sensor <b>20</b> is called major loop (master loop). The loop of using the detection of the encoder <b>21</b> is called a minor loop or a slave loop.

Next, a description will be given of an average value calculator and a memory. The average value calculator <b>40</b> corresponds to the average value calculator <b>29</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>, and calculates the average of the outputs A from the position controller <b>32</b> of predetermined period. The memory <b>42</b> corresponds to the memory <b>26</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>, and stores the average value received from the average value calculator <b>40</b>. When the belt scale sensor <b>20</b> is abnormal because of dirt, for example, the switching unit <b>33</b> switches the input terminal from the X position used in normal condition to the Y position used in an abnormal condition, and then the second comparator <b>34</b> uses the data stored in the memory <b>42</b> as the correction value.

Additionally, the detection method of an abnormal condition may be implemented using a known method such as that disclosed in JP-A No. 2004-271718, which is incorporated by reference.

<figref idref="DRAWINGS">FIG. 6</figref> is a flowchart showing an operation by the controller <b>28</b><i>a </i>of the image processing apparatus <b>100</b> according to the first example. As shown in <figref idref="DRAWINGS">FIG. 6</figref>, the controller <b>28</b><i>a </i>determines if the motor <b>14</b> has started or is starting. When the motor has started or is starting (S<b>100</b>: Yes), the controller <b>28</b><i>a </i>performs the step S<b>106</b>. When the motor does not start (S<b>100</b>: No), the controller <b>28</b><i>a </i>performs step S<b>102</b>.

In step S<b>102</b>, the controller <b>28</b><i>a </i>stops a data A acquisition timer which is used to acquire data A, and clears the data A acquisition timer. In step S<b>104</b>, the controller <b>28</b><i>a </i>clears the number of the data A acquisition.

In step S<b>106</b>, the controller <b>28</b><i>a </i>determines if the motor is starting from a stopped condition. When the motor is starting from the stopped condition (S<b>106</b>: Yes), the controller <b>28</b><i>a </i>performs step S<b>108</b>. When the motor is not starting from stopped condition, that is, the motor <b>14</b> has started (S<b>106</b>: No), the controller <b>28</b><i>a </i>performs step S<b>110</b>.

In step S<b>108</b>, the controller <b>28</b><i>a </i>starts the data A acquisition timer.

In step S<b>110</b>, the controller <b>28</b><i>a </i>determines if the count number of the data A acquisition timer exceeds X which corresponds to the predetermined period. When the controller <b>28</b><i>a </i>determines the count number of the data A acquisition timer exceeds X (S<b>110</b>: Yes), the controller <b>28</b><i>a </i>performs step S<b>114</b>. When the controller <b>28</b><i>a </i>determines the count number of the data A acquisition timer does not exceed X (S<b>110</b>: No), the controller <b>28</b><i>a </i>performs step S<b>112</b>.

In step S<b>112</b>, the data A acquisition timer, for example of the controller <b>28</b><i>a</i>, counts up. In step S<b>114</b>, the controller <b>28</b><i>a </i>acquires the data A. In step S<b>116</b>, the controller <b>28</b><i>a </i>clears the data A acquisition timer.

In step S<b>118</b>, the controller <b>28</b><i>a </i>determines if the number of the data A acquisition exceeds N which is predetermined. When the controller <b>28</b><i>a </i>determines the number of the data A acquisition exceeds N (S<b>118</b>: Yes), the controller <b>28</b><i>a </i>performs step S<b>122</b>. When the controller <b>28</b><i>a </i>determines the number of the data A acquisition does not exceed N (S<b>118</b>: No), the controller <b>28</b><i>a </i>performs step S<b>120</b>.

In step S<b>120</b>, the controller <b>28</b><i>a </i>counts up the number of the data A acquisitions.

In step S<b>122</b>, the controller <b>28</b><i>a </i>calculates the average value of the data A. Additionally, the average value of the data A is an example of a corresponding value of data A. In step S<b>124</b>, the controller <b>28</b><i>a </i>stores the average data A to the data A storing area of the memory <b>42</b>. In step S<b>126</b>, the controller <b>28</b><i>a </i>clears the number of the data A acquisition.

Additionally, the values of X and N can be arbitrary set based on the condition of the intermediate transfer belt <b>19</b>. Additionally or alternatively, the controller <b>28</b><i>a </i>can repeat step S<b>100</b> to step S<b>126</b>.

<figref idref="DRAWINGS">FIG. 7</figref> is a flowchart showing an operation by the controller <b>28</b><i>a </i>of the image forming apparatus <b>100</b> when the belt scale sensor <b>20</b> is abnormal.

As shown in <figref idref="DRAWINGS">FIG. 7</figref>, the controller <b>28</b><i>a </i>determines if the motor <b>14</b> has been started in step S<b>200</b>. When the controller <b>28</b><i>a </i>determines the motor <b>14</b> has been started, the controller <b>28</b><i>a </i>performs step S<b>202</b>. When the controller <b>28</b><i>a </i>determines the motor <b>14</b> is not started, the controller <b>28</b><i>a </i>repeats the step S<b>200</b>.

In step S<b>202</b>, the controller <b>28</b><i>a </i>determines if the belt scale sensor <b>20</b> is abnormal. When the controller <b>28</b><i>a </i>determines that the belt scale sensor <b>20</b> is abnormal (S<b>202</b>: Yes), the controller <b>28</b><i>a </i>performs the step S<b>200</b>. When the controller <b>28</b><i>a </i>determines that the belt scale sensor <b>20</b> is normal (e.g., not abnormal) (S<b>202</b>: No), the controller <b>28</b><i>a </i>performs step S<b>200</b>. In this way, the controller <b>28</b><i>a </i>monitors whether the belt scale sensor <b>20</b> is abnormal.

In step S<b>204</b>, the controller <b>28</b><i>a </i>switches the switching unit <b>33</b> so that the controlling of the surface speed of the intermediate transfer belt <b>19</b> is performed using the average value of the data A. That is, the controller <b>28</b><i>a </i>uses the average value of the data A as the outputs from the major loop. This enables a reduction in the fluctuation of the surface speed of the intermediate transfer belt <b>19</b> because of thermal expansion of the driving roller <b>16</b> when the belt scale sensor <b>20</b> is abnormal and the detection of encoder <b>21</b> is used.

Next, a description will be given of an image forming apparatus of a second example of the present invention. <figref idref="DRAWINGS">FIG. 8</figref> is a functional block diagram showing a controller <b>28</b><i>b </i>together with various units of the image forming apparatus according to a second example. The controller <b>28</b><i>b </i>corresponds to the controller <b>28</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>, and includes the CPU <b>27</b>. Incidentally, in <figref idref="DRAWINGS">FIG. 8</figref>, the same constituent parts as in <figref idref="DRAWINGS">FIG. 5</figref> are referred to by the same numerals so that description of the parts will be omitted. Moreover, the structure and function of the elements of <figref idref="DRAWINGS">FIG. 8</figref> may be implemented as the corresponding elements of <figref idref="DRAWINGS">FIG. 5</figref>.

The second comparator <b>44</b> receives the target speed, the detection of the encoder <b>21</b> (encoder speed), and the correction value which was calculated in the position controller <b>32</b> and calculates a velocity deviation. The second comparator <b>44</b> outputs the velocity deviation to the switching unit <b>46</b>. When the belt scale sensor <b>20</b> is abnormal, the switching unit <b>46</b> switches the input terminal to Y from X.

The average value calculator <b>50</b> corresponds to the average value calculator <b>29</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>, and calculates the average of the outputs B from the second comparator <b>44</b> for a predetermined period. The memory <b>52</b> corresponds to the memory <b>26</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>, and stores the average value received from the average value calculator <b>50</b>. When the belt scale sensor <b>20</b> is abnormal because of dirt, the switching unit <b>46</b> switches the input terminal from the X position used under a normal condition to the Y position used in an abnormal condition, and then the velocity controller <b>48</b> uses the data stored in the memory <b>42</b> as the velocity deviation.

The velocity controller <b>48</b> controls the output voltage output to the motor <b>14</b> corresponding to the velocity deviation from the switching unit <b>46</b> so that the surface speed of the intermediate transfer belt <b>19</b> approaches the target speed. Additionally, the velocity controller <b>48</b> may be implemented as a general controller which is designed based on a frequency response based on a motor input voltage, a signal from the encoder, and a signal from the belt scale sensor <b>20</b>.

<figref idref="DRAWINGS">FIG. 9</figref> is a flowchart showing an operation by the controller <b>28</b><i>b </i>of the image processing apparatus <b>100</b> according to a second example. Incidentally, in <figref idref="DRAWINGS">FIG. 9</figref>, the same processes as in <figref idref="DRAWINGS">FIG. 6</figref> are referred to by the same numerals so that description of the processes will be omitted.

As shown in <figref idref="DRAWINGS">FIG. 9</figref>, the controller <b>28</b><i>b </i>determines if the motor <b>14</b> has started or is starting in step S<b>100</b>. When the motor has started or is starting (S<b>100</b>: Yes), the controller <b>28</b><i>b </i>performs step S<b>106</b>. When the motor does not start (S<b>100</b>: No), the controller <b>28</b><i>b </i>performs step S<b>302</b>.

In step S<b>302</b>, the controller <b>28</b><i>b </i>stops a data B acquisition timer which is used to acquire data B, and clears the data B acquisition timer. In step S<b>304</b>, the controller <b>28</b><i>b </i>clears the number of the data B acquisition.

In step S<b>106</b>, the controller <b>28</b><i>b </i>determines if the motor is starting from a stopped condition. When the motor is starting from a stopped condition (S<b>106</b>: Yes), the controller <b>28</b><i>b </i>performs step S<b>308</b>. When the motor is not starting from a stopped condition, that is, the motor <b>14</b> has started (S<b>106</b>: No), the controller <b>28</b><i>b </i>performs step S<b>310</b>. In step S<b>308</b>, the controller <b>28</b><i>b </i>starts the data B acquisition timer.

In step S<b>310</b>, the controller <b>28</b><i>b </i>determines if the count number of the data B acquisition timer exceeds X which corresponds to the predetermined period. When the controller <b>28</b><i>b </i>determines the count number of the data B acquisition timer exceeds the X (S<b>310</b>: Yes), the controller <b>28</b><i>b </i>performs step S<b>314</b>. When the controller <b>28</b><i>b </i>determines the count number of the data B acquisition timer does not exceed X (S<b>310</b>: No), the controller <b>28</b><i>b </i>performs step S<b>312</b>.

In step S<b>312</b>, the controller <b>28</b><i>b </i>causes the data B acquisition timer counts up. In step S<b>314</b>, the controller <b>28</b><i>b </i>acquires the data B. In step S<b>316</b>, the controller <b>28</b><i>b </i>clears the data B acquisition timer.

In step S<b>318</b>, the controller <b>28</b><i>b </i>determines if the number of data B acquisitions exceeds N which is predetermined. When the controller <b>28</b><i>b </i>determines the number of data B acquisition exceeds N (S<b>318</b>: Yes), the controller <b>28</b><i>b </i>performs step S<b>322</b>. When the controller <b>28</b><i>b </i>determines the number of data B acquisition does not exceed N (S<b>318</b>: No), the controller <b>28</b><i>b </i>performs step S<b>320</b>.

In step S<b>320</b>, the controller <b>28</b><i>b </i>causes the count of the number of data B acquisition to increase by one. In step S<b>322</b>, the controller <b>28</b><i>b </i>calculates the average value of data B. Additionally, the average value of data B is an example of a corresponding value of data B.

In step S<b>324</b>, the controller <b>28</b><i>b </i>stores the average value of data B to the data B storing area of the memory <b>52</b>. In step S<b>326</b>, the controller <b>28</b><i>b </i>clears the number of data B acquisitions.

Additionally, the values of X and N can be arbitrarily set based on a condition of the intermediate transfer belt <b>19</b>. The controller <b>28</b><i>b </i>repeats from step S<b>100</b> to step S<b>326</b>.

<figref idref="DRAWINGS">FIG. 10</figref> is a flowchart showing an operation by the controller <b>28</b><i>b </i>of the image forming apparatus <b>100</b> when a belt scale sensor <b>20</b> is abnormal. In <figref idref="DRAWINGS">FIG. 10</figref>, steps S<b>200</b> and S<b>202</b> are the same as the corresponding steps of <figref idref="DRAWINGS">FIG. 7</figref>, and the description of those steps is omitted.

In step S<b>404</b>, the controller <b>28</b><i>b </i>switches the switching unit <b>46</b> of <figref idref="DRAWINGS">FIG. 8</figref> which is used for controlling the surface speed of the intermediate transfer belt <b>19</b> using the average value of data B. This enables the reduction of fluctuation of the surface speed of the intermediate transfer belt <b>19</b> because of thermal expansion of the driving roller <b>16</b> when the belt scale sensor <b>20</b> is abnormal and the detection of the encoder <b>21</b> is used.

Next, a description is provided of a modified example of the present invention which uses the temperature information. <figref idref="DRAWINGS">FIG. 11</figref> is a functional block diagram showing the belt driving controlling unit <b>22</b> which controls the intermediate transfer belt together with various units of the image forming apparatus according to a modified example. In <figref idref="DRAWINGS">FIG. 11</figref>, the same constituent parts as in <figref idref="DRAWINGS">FIG. 3</figref> are referred to by the same numerals and a description of the corresponding parts is omitted. A thermistor <b>24</b> (a temperature detecting unit) is arranged near the driving roller <b>16</b>, and detects the temperature around or surrounding the driving roller <b>16</b>. The thermistor <b>24</b> outputs a signal based on the detected temperature to the CPU <b>27</b>.

A description is provided of the controller <b>28</b><i>a </i>and the controller <b>28</b><i>b </i>which perform based on the signal from the thermistor <b>24</b>. <figref idref="DRAWINGS">FIGS. 12A and 12B</figref> are illustrations showing how to store data in the memory and <b>52</b> (or the memory <b>26</b>). <figref idref="DRAWINGS">FIG. 12A</figref> is an illustration showing addresses of the memory <b>42</b> when the controller <b>28</b><i>a </i>stores the average value of the data A. <figref idref="DRAWINGS">FIG. 12B</figref> is an illustration showing addresses of the memory <b>52</b> when the controller <b>28</b><i>b </i>stores the average value of the data B. In this way, the average value of the data A and the average value of the data B are stored to different areas corresponding to each temperature ranges.

<figref idref="DRAWINGS">FIG. 13</figref> is a flowchart showing an operation by the controller <b>28</b><i>a </i>based on the average of the data A corresponding to each temperature range according to a modified example of the first example. Incidentally, in <figref idref="DRAWINGS">FIG. 13</figref>, the same steps as those illustrated in <figref idref="DRAWINGS">FIG. 6</figref> are referred to by the same numerals and a description of those steps is omitted.

In step S<b>524</b>, the controller <b>28</b><i>a </i>stores the average value of the data A to area of the memory <b>42</b> corresponding to temperature when the average value is calculated.

<figref idref="DRAWINGS">FIG. 14</figref> is a flowchart showing an operation by the controller <b>28</b><i>a </i>according to the modified example of the first example of the present invention when the belt scale sensor <b>20</b> is abnormal. In <figref idref="DRAWINGS">FIG. 14</figref>, the same steps as in <figref idref="DRAWINGS">FIG. 7</figref> are referred to by the same numerals and the description of those steps is omitted.

In step S<b>600</b>, the controller <b>28</b><i>a </i>determines if the average value of the data A is stored in the area of the memory <b>42</b> corresponding to the current temperature. When the controller <b>28</b><i>a </i>determines that the average value of the data A is stored in the area of the memory <b>42</b> corresponding to the current temperature (S<b>600</b>: Yes), the controller <b>28</b><i>a </i>performs step S<b>602</b>. When the controller <b>28</b><i>a </i>determines that the average value of the data A is not stored the area of the memory <b>42</b> corresponding to the current temperature (S<b>600</b>: No), the controller <b>28</b><i>a </i>performs the step S<b>200</b>.

In step S<b>602</b>, the controller <b>28</b><i>a </i>switches the switching unit <b>33</b> so as using the average of the data A corresponding to the current temperature. This enables the controller <b>28</b><i>a </i>to reduce the fluctuating of the surface speed of the intermediate transfer belt <b>19</b> when the belt scale sensor <b>20</b> is abnormal and the detection of encoder <b>21</b> is used, because the controller <b>28</b><i>a </i>can use the average value of the data A corresponding to the current temperature, that is, corresponding to the expansion level of the driving roller <b>16</b>.

Additionally, when the controller <b>28</b><i>a </i>determines that the average value of the data A is not stored in the area of the memory <b>42</b> corresponding to current temperature, the controller <b>28</b><i>a </i>may use the average value of data A which is stored in the area of memory <b>42</b> corresponding to the temperature being close to the current temperature.

<figref idref="DRAWINGS">FIG. 15</figref> is a flowchart showing an operation by the controller <b>28</b><i>b </i>based on average of the data B corresponding to each temperature range according to a modified example of the second example. In <figref idref="DRAWINGS">FIG. 15</figref>, the same steps as illustrated in <figref idref="DRAWINGS">FIG. 9</figref> are referred to by the same numerals and a description of these steps is omitted.

In step S<b>724</b>, the controller <b>28</b><i>b </i>stores the average value of the data B to an area of the memory corresponding to temperature when the average value is calculated.

<figref idref="DRAWINGS">FIG. 16</figref> is a flowchart showing an operation by the controller <b>28</b><i>b </i>according to a modified example of the second example of the present invention when the belt scale sensor <b>20</b> is abnormal. In <figref idref="DRAWINGS">FIG. 16</figref>, the same steps as illustrated in <figref idref="DRAWINGS">FIG. 10</figref> are referred to by the same numerals and a description of these steps is omitted.

In step S<b>600</b>, the controller <b>28</b><i>b </i>determines if the average value of the data B is stored in the area of the memory <b>52</b> corresponding to current temperature. When the controller <b>28</b><i>b </i>determines that the average value of the data B is stored the area of the memory <b>52</b> corresponding to current temperature (S<b>600</b>: Yes), the controller <b>28</b><i>b </i>performs step S<b>802</b>. When the controller <b>28</b><i>b </i>determines that the average value of the data B is not stored the area of the memory <b>52</b> corresponding to current temperature (S<b>600</b>: No), the controller <b>28</b><i>b </i>performs the step S<b>200</b>.

In the step S<b>802</b>, the controller <b>28</b><i>b </i>switches the switching unit <b>46</b> to use the average of the data B corresponding to current temperature. This enables the controller <b>28</b><i>b </i>to reduce the fluctuation of the surface speed of the intermediate transfer belt <b>19</b> when the belt scale sensor <b>20</b> is abnormal and the detection of encoder <b>21</b> is used, because the controller <b>28</b><i>b </i>can use the average value of the data B corresponding to the current temperature, that is, corresponding to the expansion level of the driving roller <b>16</b>.

Additionally, when the controller <b>28</b><i>b </i>determines that the average value of the data B is not stored the area of the memory <b>52</b> corresponding to the current temperature, the controller <b>28</b><i>b </i>may use the average value of data B which is stored in the area of memory <b>52</b> corresponding to the temperature which is close to current temperature.

Additionally, the memory <b>26</b> (the memory <b>42</b>, the memory <b>52</b>) and the average value calculator <b>29</b> (the average value calculator <b>40</b>, the average value calculator <b>50</b>) may be arranged in the image forming apparatus <b>100</b>. When the DFE <b>12</b> is connected to the image forming apparatus <b>100</b>, the memory and average value calculator may be arranged in the DFE <b>12</b>, or one of them may be arranged in the DFE <b>12</b>, the other may be arranged in the image forming apparatus <b>100</b>. The each units of the controller <b>28</b> (the controller <b>28</b><i>a</i>, the controller <b>28</b><i>b</i>) may be configured in software, may be configured in hardware, or may be a combination of hardware and software.

In the foregoing description of the embodiments, a description was given that the corresponding value of data A or B is the average value of data A or B. However, the corresponding value may be another value. The belt conveyance apparatus is not limited to an apparatus including an intermediate transfer belt, may be an apparatus including a photoconductive belt which conveys an electrostatic latent image or a conveyance belt which conveys the sheet such as paper or a document or the like.

The invention may be implemented using one or more circuits or processing circuits. A circuit or processing circuit is a structural assemblage of electronic components including conventional circuit elements, integrated circuits including application specific integrated circuits, standard integrated circuits, application specific standard products, and field programmable gate arrays. Further a processing circuit includes central processing units, graphics processing units, and microprocessors which are programmed or configured according to software code. A circuit does not include pure software, although a circuit does includes the above-described hardware executing software.

The memories described herein may be implemented using any desired and appropriate technology including a RAM, ROM, SRAM, flash memory, semiconductor memory, a hard disk drive, or any other type of memory which is desired to be used.

The foregoing description of the embodiments of the invention has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above teachings. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.